Question about voltage and Copy Cad

I'm experimenting with my Copy Cad kit (1 gallon). The power supply that comes with the kit has several voltage settings (1.5 V through 12 V). Which should I be using and why?

I also have a battery charger that can supply 2, 6 or 10 Amps at 6 or 12 volts. I was hoping to use this to plate some larger items.

Also, when I was experimenting last night with the kit, I dropped in a piece of black pipe to "purify" the solution as the instructions say (I glass beaded the pipe and degreased it with acetone first). I attached the power supply, and the anode started to bubble as it should. Out of curiosity, I switched the power supply from 1.5 to 3 volts, and the power supply started to smoke slightly.

I figured that perhaps the part was too large and did some calculations. I found that I had about 28 square inches (inside and outside of the pipe), which is about twice what the power supply can handle, so I hooked up my battery charger at 2 amps, but there was no bubbling with that setup. Should I have added some light bulbs or something in the circuit, even though 2 amps should have been about right for that part? Help!

Sorry for all the questions, but can anyone explain some of the voltage requirements? Thanks in advance.

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